Sleeping Beauty Transposon System
Introduction The Sleeping Beauty (SB) Transposon is essentially an artificial DNA transposon used in horizontal gene transfer that utilizes synthetic expression cassettes. It is a member of the super family of Tc1/mariner transposons. In the SB Transposon System (SBTS), synthetic DNA transposons are designed in order to introduce new genes and functions into vertebrate animals by inserting specific DNA sequences into chromosomes. The SB transposon is a non-viral integration vector system that has been proven to be effective for gene transfer as well as functional genomics. The SB Transposon System has been one of the most effective non-viral vectors for gene therapy. The advantages of non-viral vectors such as SBTS include low costs, ease of production, stability during storage, and lack of immune response once inside the host cells. Non-viral gene therapies prior to SBTS experienced problems in the expression of transgene in host organisms and the efficacy of sustained gene expression. SBTS solves these issues because it combines the advantages of viruses and naked DNA. The Sleeping Beauty Transposon System has been approved for stem cell ex vivo gene therapy, and in particular, T-cells to treat lymphoma. Potential therapeutic applications include delivery of the SB transposons to the liver to treat hemophilia and mucopolysaccharidoses type I and VII. Mechanism The SBTS consists of two parts: a transposon that contains a gene-expression cassette and a source of transposase enzyme. When the expression cassette is transposed from a plasmid into the genome of the host, the transcription of the transgene can be sustained. The SB transposon is designed to carry DNA sequences for insertion into chromosomal DNA. These encode transgenes that are integrated into the genome for sustained therapeutic expression. DNA transposons will translocate in a cut-and-paste way from one DNA location to a TA sequence in the host DNA. SB transposase cuts the transposon out of the plasmid and inserts it on the TA sequence. The SB transposon is in the plasmid along with the therapeutic gene. The delivery of the gene varies depending on whether the cell is in a culture or in a tissue. If the transposon system is in a cell culture, then electroporation or transfection is used for delivery. If the transposon system is in a tissue, then hydrodynamic injection is used for delivery. The source of the transposase is a gene that is either in the same plasmid as the transposon or a different plasmid similar to the one holding the transposon. Applications Over the last 10 years, SB transposons have been widely used for gene therapy. In addition, they can be used to discover the functionality of various genes, especially cancer-causing genes. The genes that can be inactivated by transposon insertion are called "knocked out" genes. The genetic cargo that is transposed is an expression cassette, which consists of a transgene and other elements that would deliver designed transcriptional effects of the transgene in host cells. Sleeping beauty transposons have great potential for human gene therapy, especially given its affordability. Currently, SBTS is in clinical trials for treatment of lymphoma by genetically modifying T cells. References 1. "Sleeping Beauty Transposon System." Wikipedia. Wikimedia Foundation, 24 Oct. 2014. Web. 17 Nov. 2014. 2. Aronovich, E. L., R. S. Mcivor, and P. B. Hackett. "The Sleeping Beauty Transposon System: A Non-viral Vector for Gene Therapy." Human Molecular Genetics 20.R1 (2011): R14-20. PubMed. Web. 17 Nov. 2014. PMID: 21459777